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Cloud Seeding 07-15-15 BOARD Agenda Item 9 Cloud Seeding Presented by: Frank McDonough – Meteorologist Page 1 of 32 Outline 07-15-15 BOARD Agenda Item 9 - Background - Brief Tahoe Summary - Cloud seeding technology (table) Page 2 of 32 Background 07-15-15 BOARD Agenda Item 9 Page 3 of 32 Background 07-15-15 BOARD Agenda Item 9 Create small ice crystals Subfreezing liquid through seeding water clouds present – no precipitation DRI generator Crystals grow in presence of tiny subfreezing drops Crystals grow into large Snow crystals melts into which fall runoff as snow and add to Truckee River snowpack Page 4 of 32 CA/NV cloud seeding projects07-15-15 BOARD Agenda Item 9 West Coast operational cloud seeding projects over the past 20 years. Currently active in 11 to 14 watersheds Aircraft and ground-based Page 5 of 32 Idaho Cloud Seeding 07-15-15 BOARD Agenda Item 9 $1 million/ year Aircraft cloud seeding warmer winter storms Ground-based and aircraft cloud seeding for colder storms Page 6 of 32 Utah cloud seeding projects07-15-15 BOARD Agenda Item 9 Most of the higher terrain in the state is targeted. Page 7 of 32 Tahoe/Truckee seeding network07-15-15 BOARD Agenda Item 9 CSG Page 8 of 32 DRI cloud seeding 07-15-15 BOARD Agenda Item 9 Sited at locations that maximize seeding effectiveness Remote 24/7 operations by expert cloud seeding meteorologists DRI Cloud seeding generator: Generators and Ward (Sierra Crest near Alpine) communications equipment are reliable and serviced by experienced technicians Page 9 of 32 Tahoe/Truckee – 5 year SWE 07-15-15 BOARD Agenda Item 9 Sierra Crest Squaw (8,200’) Echo Pk (7,600’) Page 10 of 32 Tahoe/Truckee – 5 year SWE 07-15-15 BOARD Agenda Item 9 Truckee (6,400’) Big Meadow (8,300’) Page 11 of 32 07-15-15 BOARD Agenda Item 9 Cloud Seeding Truckee/Tahoe WY 2015 Summary of season - 19 events year to date Nov 2014 – 4 events Dec 2014 - 6 events Jan 2015 - 1 event Feb 2015 - 2 events Mar 2015 - 2 events Apr 2015 - 4 events -Total Generator hours – 590 gen-hours -Initial estimate of increase in snow water equivalent (SWE) ~9,000 acre-feet Page 12 of 32 Tahoe/Truckee – February 201507-15-15 BOARD Agenda Item 9 3 Storms: Feb 6-7 4” SWE T -2C Winds (SW/80MPH) No Seed Feb 8-9 4” SWE T 0C -> -6C Winds (SW-W/60MPH) Seed 2nd half of storm (unstable) Feb 27-28 1.7” SWE T -8C Winds (W/15MPH) Seed entire event Page 13 of 32 07-15-15 BOARD Agenda Item 9 Cloud Seeding Truckee/Tahoe WY 2015 WY 2015 compared to previous years Mean generator hours Historic: 917 gen-hours WY2015: 590 gen-hours Mean seeding water augmentation Historic: 14,600 acre-feet WY2015: ~9,000 acre-feet* Median cost per acre-ft. Historic: < $20 *9,000 acre-ft. is enough water for 21,000 Truckee Meadows households. Page 14 of 32 07-15-15 BOARD Agenda Item 9 Cloud Seeding Truckee/Tahoe WY 2015 Tahoe Summary - Very warm and dry winter overall - All seedable storms were seeded - Equipment worked well when needed - Estimated 9000 acre-feet (3 billion gallons) of water added to snow pack - Several big storms (Pineapple express) were too warm to cloud seed from ground using AgI - Aircraft - Liquid Propane Page 15 of 32 07-15-15 BOARD Agenda Item 9 Seeding Description Pro’s Con’s Productivity Cost Method Remote: Use AgI plume - Continuous - Colder than - 10000 – $60,000/generat Ground released from operation 6oC (21oF) 20000 acre-ft or: includes based surface to seed - Low Cost - Requires season install/full, (AgI*) clouds - Solar powered specific set of forecasting and - In or below cloud atmospheric seeding base conditions operations, - Proven reporting technology Aircraft Release AgI from - Max increase in - Higher cost ~200+ acre- $20,000 mo (AgI*) aircraft flares precipitation - No ft/hr (in ideal aircraft/crew, directly into - Warmer storms continuous conditions) $800/hr seeding clouds - More seeding operations operations options (winds) (pilot $ rest/refuel) forecasting/flight - Aircraft Icing guidance Remote: Create ice -Warmer storms - - In cloud Expected to $13,000 to build Propane crystals at nozzle 2oC (29oF) operations be significant and fill, use crystals to - Low Cost - High (Utah study) $ id site and seed cloud - Solar Powered elevation sites but requires install (variable) (access) further study $ operations - Experimental after *AgI – silver iodide operations Page 16 of 32 Thank You ! 07-15-15 BOARD Agenda Item 9 Any questions/comments? Carson Spur Feb 2011 Page 17 of 32 Extra slides 07-15-15 BOARD Agenda Item 9 Silver Iodide (AgI) -Insoluble in water (remains a solid at high and low temperatures) -No molecular charge -Less than 1 oz released per hour by DRI generators – dispersed over 35 sq. miles -Not bioavailable (is not biologically available to the ecosystem) -The amounts found in the seeded snow < 10 pts trillion (10/1000000000000) (Huggins 2015) -Not detectable in soil/runoff or water bodies even after 50 years of cloud seeding (Mokelumne; Stone 2006) Page 18 of 32 Is cloud seeding effective?07-15-15 BOARD Agenda Item 9 Cloud seeding can increase snowfall by up to 15% (peer reviewed scientific publications) - Climax Experiments Colorado (central Colorado Mountains) (Mielke et al. 1981; Grant 1986) - Bridger Range Experiments (15%) ( southwestern Montana) (Super and Heimbach 1983) - Snowy Precipitation Enhancement Research Project (14%) (Snowy Mountains, Australia) (Manton et al. 2011) - Wyoming Weather Modification Pilot Project (5 to 15%) (Medicine Bow/Sierra Madre, WY) $15M, 10 years (Breed et al. 2014) Page 19 of 32 07-15-15 BOARD Agenda Item 9 Wyoming Weather Modification Pilot Program summarized from Roy Rasmussen’s 2015 AMS presentation presented by Frank McDonough Page 20 of 32 07-15-15 BOARD Agenda Item 9 Wyoming WMPP - Summary Medicine Bow Sierra Madre Page 21 of 32 07-15-15 BOARD Agenda Item 9 Experiment Area target target (from Rasmussen et. al. 2015)Page 22 of 32 07-15-15 BOARD Agenda Item 9 Random Seeding Experiment (RSE) SM seeded MB seeded Page 23 of 32 07-15-15 BOARD Agenda Item 9 RRR equation – Statistics Primary Test Statistic for the Statistical Evaluation Root Regression Ratio (RRR) RRR = (Seeded Snowfall/Unseeded Snowfall) with adjustments using controls which would provide an estimate of snowfall that would have occurred naturally Page 24 of 32 Primary Results 07-15-15 BOARD Agenda Item 9 (from Rasmussen et. al. 2015) Page 25 of 32 07-15-15 BOARD Agenda Item 9 Downwind Contamination AgI acoustic counter 18 of 118 cases found to have downwind contamination (from Rasmussen et. al. 2015) Page 26 of 32 07-15-15 BOARD Agenda Item 9 Downwind Contamination (from Rasmussen et. al. 2015) Page 27 of 32 07-15-15 BOARD Agenda Item 9 Generator Hours Not all generators operated for all cases. Leads to target area not getting seeded. Remove cases when generators-hours less than 21-hr of 32-hr possible. (from Rasmussen et. al. 2015) Page 28 of 32 07-15-15 BOARD Agenda Item 9 Generator Hours (from Rasmussen et. al. 2015) Page 29 of 32 Numerical Model Simulations07-15-15 BOARD Agenda Item 9 High-resolution model run over 3 -winters Modeling results of half of cases suggests 10 – 15% increase in seeded Page 30 of 32 model snowfall compared to unseeded model snowfall (from Rasmussen et. al. 2015) Conclusion 07-15-15 BOARD Agenda Item 9 (from Rasmussen et. al. 2015) Page 31 of 32 Moving Forward 07-15-15 BOARD Agenda Item 9 Based on positive results Wyoming investing over $1 million to explore/conduct cloud seeding in other areas of the state Page 32 of 32.
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